Using Insights from Psychology and Language to Improve How People Reason with Description Logics

Inspired by insights from theories of human reasoning and language, we propose additions to the Manchester OWL Syntax to improve comprehensibility. These additions cover: functional and inverse functional properties, negated conjunction, the definition of exceptions, and existential and universal restrictions. By means of an empirical study, we demonstrate the effectiveness of a number of these additions, in particular: the use of solely to clarify the uniqueness of the object in a functional property; the replacement of and with intersection in conjunction, which was particularly beneficial in negated conjunction; the use of except as a substitute for and not; and the replacement of some with including and only with noneOrOnly, which helped in certain situations to clarify the nature of these restrictions

Coherent spin manipulation in an exchange-only qubit

Initialization, manipulation, and measurement of a three-spin qubit are demonstrated using a few-electron triple quantum dot, where all operations can be driven by tuning the nearest-neighbor exchange interaction. Multiplexed reflectometry, applied to two nearby charge sensors, allows for qubit readout. Decoherence is found to be consistent with predictions based on gate voltage noise with a uniform power spectrum. The theory of the exchange-only qubit is developed and it is shown that initialization of only two spins suffices for operation. Requirements for full multi-qubit control using only exchange and electrostatic interactions are outlined.Comment: related work at http://marcuslab.harvard.ed

PG 1700+518 Revisited: Adaptive Optics Imaging and a Revised Starburst Age for the Companion

We present the results of adaptive-optics imaging of the z=0.2923 QSO PG 1700+518 in the J and H bands. The extension to the north of the QSO is clearly seen to be a discrete companion with a well-defined tidal tail, rather than a feature associated with the host galaxy of PG 1700+518 itself. On the other hand, an extension to the southwest of the QSO (seen best in deeper, but lower-resolution, optical images) does likely comprise tidal material from the host galaxy. The SED derived from images in J, H, and two non-standard optical bands indicates the presence of dust intermixed with the stellar component. We use our previously reported Keck spectrum of the companion, the SED found from the imaging data, and updated spectral-synthesis models to constrain the stellar populations in the companion and to redetermine the age of the starburst. While our best-fit age of 0.085 Gyr is nearly the same as our earlier determination, the fit of the new models is considerably better. This age is found to be remarkably robust with respect to different assumptions about the nature of the older stellar component and the effects of dust.Comment: 11 pages; includes two eps figures. Latex (AASTEX). Two additional figures in gif format. Postscript version including all figs. (424 kb) can be obtained from http://www.ifa.hawaii.edu/~canaguby/preprints.html To appear in ApJ. Letter

Hyperfine-mediated gate-driven electron spin resonance

An all-electrical spin resonance effect in a GaAs few-electron double quantum dot is investigated experimentally and theoretically. The magnetic field dependence and absence of associated Rabi oscillations are consistent with a novel hyperfine mechanism. The resonant frequency is sensitive to the instantaneous hyperfine effective field, and the effect can be used to detect and create sizable nuclear polarizations. A device incorporating a micromagnet exhibits a magnetic field difference between dots, allowing electrons in either dot to be addressed selectively.Comment: related papers available at http://marcuslab.harvard.ed

Measurement of Temporal Correlations of the Overhauser Field in a Double Quantum Dot

In quantum dots made from materials with nonzero nuclear spins, hyperfine coupling creates a fluctuating effective Zeeman field (Overhauser field) felt by electrons, which can be a dominant source of spin qubit decoherence. We characterize the spectral properties of the fluctuating Overhauser field in a GaAs double quantum dot by measuring correlation functions and power spectra of the rate of singlet-triplet mixing of two separated electrons. Away from zero field, spectral weight is concentrated below 10 Hz, with 1/f^2 dependence on frequency, f. This is consistent with a model of nuclear spin diffusion, and indicates that decoherence can be largely suppressed by echo techniques.Comment: related papers available at http://marcuslab.harvard.ed

Effect of Exchange Interaction on Spin Dephasing in a Double Quantum Dot

We measure singlet-triplet dephasing in a two-electron double quantum dot in the presence of an exchange interaction which can be electrically tuned from much smaller to much larger than the hyperfine energy. Saturation of dephasing and damped oscillations of the spin correlator as a function of time are observed when the two interaction strengths are comparable. Both features of the data are compared with predictions from a quasistatic model of the hyperfine field.Comment: see related papers at http://marcuslab.harvard.ed

Conditional operation of a spin qubit

We report coherent operation of a singlet-triplet qubit controlled by the arrangement of two electrons in an adjacent double quantum dot. The system we investigate consists of two pairs of capacitively coupled double quantum dots fabricated by electrostatic gates on the surface of a GaAs heterostructure. We extract the strength of the capacitive coupling between qubit and double quantum dot and show that the present geometry allows fast conditional gate operation, opening pathways to multi-qubit control and implementation of quantum algorithms with spin qubits.Comment: related papers here: http://marcuslab.harvard.ed

Scale-freeness for networks as a degenerate ground state: A Hamiltonian formulation

The origin of scale-free degree distributions in the context of networks is addressed through an analogous non-network model in which the node degree corresponds to the number of balls in a box and the rewiring of links to balls moving between the boxes. A statistical mechanical formulation is presented and the corresponding Hamiltonian is derived. The energy, the entropy, as well as the degree distribution and its fluctuations are investigated at various temperatures. The scale-free distribution is shown to correspond to the degenerate ground state, which has small fluctuations in the degree distribution and yet a large entropy. We suggest an implication of our results from the viewpoint of the stability in evolution of networks.Comment: 7 pages, 3 figures. To appear in Europhysics lette

Focusing in Asynchronous Games

Game semantics provides an interactive point of view on proofs, which enables one to describe precisely their dynamical behavior during cut elimination, by considering formulas as games on which proofs induce strategies. We are specifically interested here in relating two such semantics of linear logic, of very different flavor, which both take in account concurrent features of the proofs: asynchronous games and concurrent games. Interestingly, we show that associating a concurrent strategy to an asynchronous strategy can be seen as a semantical counterpart of the focusing property of linear logic

The Orbit of the Companion to HD 100453A: Binary-Driven Spiral Arms in a Protoplanetary Disk

HD 100453AB is a 10+/-2 Myr old binary whose protoplanetary disk was recently revealed to host a global two-armed spiral structure. Given the relatively small projected separation of the binary (1.05", or ~108 au), gravitational perturbations by the binary seemed to be a likely driving force behind the formation of the spiral arms. However, the orbit of these stars remained poorly understood, which prevented a proper treatment of the dynamical influence of the companion on the disk. We observed HD 100453AB between 2015-2017 utilizing extreme adaptive optics systems on the Very Large Telescope and Magellan Clay Telescope. We combined the astrometry from these observations with published data to constrain the parameters of the binary's orbit to a=1.06"+/-0.09", e=0.17+/-0.07, and i=32.5+/- 6.5 degrees. We utilized publicly available ALMA CO data to constrain the inclination of the disk to i~28 degrees, which is relatively co-planar with the orbit of the companion and consistent with previous estimates from scattered light images. Finally, we input these constraints into hydrodynamical and radiative transfer simulations to model the structural evolution of the disk. We find that the spiral structure and truncation of the circumprimary disk in HD 100453 are consistent with a companion-dirven origin. Furthermore, we find that the primary star's rotation, its outer disk, and the companion exhibit roughly the same direction of angular momentum, and thus the system likely formed from the same parent body of material.Comment: 28 pages, 11 figures, Accepted to Ap